1. Statement of the Technical Field
The inventive arrangements relate generally to RF switches, and more particularly to high density microwave switch architectures.
2. Description of the Related Art
RF/microwave switches are used in a wide variety of applications. For example, they can be used for switching multiple inputs to multiple outputs, routing of RF signals, selecting a particular input for a device from among multiple input signal sources, and switching a particular device into and out of a circuit. Various techniques are known for implementing RF switching. For example, PIN diodes are often used for this purpose. Developments in Micro-Electro-Mechanical Systems (MEMS) also include RF switching devices that demonstrate useful performance at microwave frequencies. A number of different switch topologies are available for MEMS RF switches. In general, these devices offer lower insertion loss, consume less power, and offer higher linearity as compared to other similar sized devices. Still, existing single pole multiple throw switches for RF and microwave applications of any dimension are often limited with regard to the number of throws that can be provided without adversely affecting switch performance. Increasing the number of paths often tends to degrade the switch performance and increase switch size. These are important design considerations since RF performance and switch density are two critical requirements for many military, industrial, and commercial applications.
One performance limiting factor for single-pole multiple-throw (SPMT) and multiple-pole multiple-throw (MPMT) type RF switches arises from relatively long stub lengths as compared to wavelength of interest. Long stub lengths required for communicating RF to and from MEMS switches tends to be largely unavoidable in current architectures due to the generally planar layout of such devices. Close spacing of MEMS switches in particular also can be a problem because of the difficulty associated with shielding actuation mechanisms. For example, actuation of one magnetically actuated switch can inadvertently result in activation of an adjacent switch.
As a result of these and other difficulties, the largest value of N for a single pole N throw switch manufactured from conventional mechanical relays is presently about 14. Architectures for MEMS type SPMT and MPMT switches have generally included flat and layered architectures. Layered architectures generally are designed around 2-dimensional stripline layouts with coaxial layer interconnects. However, even these layered MEMS designs have not managed to increase the number of throws beyond about 14 without significant performance degradation, size and cost penalties.